Year	% of land area
1990	0.4618608712525468
1991	0.4565829048219656
1992	0.4513049383913845
1993	0.4460269719608033
1994	0.4407490055302222
1995	0.435471039099641
1996	0.43019307266905993
1997	0.4249151062384787
1998	0.4196371398078975
1999	0.4143591733773164
2000	0.4090812069467352
2001	0.4038032405161541
2002	0.3985252740855729
2003	0.3932473076549917
2004	0.3879693412244106
2005	0.3826913747938295
2006	0.37741340836324827
2007	0.3721354419326671
2008	0.366857475502086
2009	0.3615795090715048
2010	0.3563015426409237
2011	0.35102357621034247
2012	0.3457456097797613
2013	0.34046764334918017
2014	0.335189676918599
2015	0.3299117104880179
2016	0.3246337440574367
2017	0.319394586203551
2018	0.3140584069079267
2019	0.30881924905404096
2020	0.30348306975841666
2021	0.29821160376443195